Pump



March 5, 1968 J. CHAMBERS 3,371,618

PUMP

Filed Feb. 18, 1966 s Sheets-Sheet 1 LOW 2 23 11- INVENTOR Joli/vCHAMBERS MM, 7% 7w 9 .5

ATTORNEY 5 March 5, 1968 J. CHAMBERS 3,371,618

PUMP I Filed Feb. 18. 1966 e Sheets-Sheet 2 -l3| SECONDARY FLOW :21

MiXED FLUIDS E2 -'III7/III/ IIIV/IIII'IIII/II/7 MIXED m- FLUIDS xllpxqln' llx'ai 53 MIXED FLUIDS 'IIIIIIIIIIIIIIIIIIIIIIIIIIIN' INVENTORJOHN CHAMBERS BY MMWM 7 5 ATTORNEY 5 March 5, 1968 J. CHAMBERS 3,371,618

PUMP

Filed Feb. 18. 1966 6 Sheets-Sheet .5

INVENTOR JOHN CHAMBERS BY Mywm A'ITO NEYS J. CHAMBERS March 5, 1968 PUMP'6 Sheets-Sheet 5 Filed Feb. 18, 1966 CONSTANT PRESSURE STRAIGHT 6DISTANCE FRCM NOZZLE- INCHES 4 PRESSURE TAP- NUMBERS INVENTOR JOHNCHAMBERS BY 77m 9 5 WM'M WRNEYS,

March 5,1968

Filed Feb. 18. 1966 J-CHAMBERS MDGNG SECHON PUMP MFFUSER MDGNG QQI:

DRWE

SECTDN MFFUSER I 6 Sheets-Sheet 6 United States Patent PUM JohnChambers, Rte. 1, Box M41, Del Mar, Calif. 92014 Filed Feb. 18, 1966,Ser. No. 528,464 11 Claims. (Cl. 103-258) ABSTRACT OF THE DISCLOSUREThis invention relates to improvements in jet pumps and morespecifically to improvements in jet pumps which minimize or eliminatethe energy losses attributable to expansion of the primary or motivefluid and/oiof the secondary or induced fluid in the mixing chamberwhere the latter becomes entrained in the former.

Jet pumps have particular utility as condensers, mixers and fluidcirculating apparatus where it is desired to modify the temperature ofthe circulating fluid or to mix fluids having different physicalcharacteristics. A major difficulty, however, with existing jet pumps isthat satisfactory mixing of the primary and secondary fluids cannot beattained without high energy losses due to expansion of the motive fluidand turbulence at the contact region of the fluids in the mixingchamber.

Known jet pump constructions of both the single and plural secondaryfluid inlet types are exemplified by United States Patent No. 571,022issued Nov. 10, 1896 to L. Schutte for Exhauster and United StatesPatent No. 1,111,541 issued Sept. 221914 to E. Koerting for Injector.The effectiveness of the plural secondary inlets is, in the Schutte andKoerting devices however, partially lost by the use of improperlydesigned mixing chambers. Primary fluid exiting from the pump nozzle hasa low static pressure and expands outwardly toward the sides of themixing chamber in a conical configuration. The straight-walledcylindrical mixing chamber retards expansion of the escaping primaryfluid which intercepts the chamber side walls before complete mixing isaccomplished and, thus, decreases its axial velocity and raises itsstatic pressure a short distance axially from the nozzle. The secondaryfluid entrance openings farthest spaced axially from the nozzle, thus,do not contribute efficiently to the mixing operation. For maximumetficiency,

the static pressure of the drive and driven fluids in the mixing chamberand the static pressure of the drive fluid should be constant throughoutthe length of the mixing chamber and, approach but be slightly above thedrive fluid vapor pressure. Such a constant pressure is impossible tomaintain throughout a cylindrical, diverging or improperly designedconverging mixing chamber.

Also, although the Schutte suction inlets are inclined in the directionof primary fluid flow, once the secondary fluid enters the mixingchamber a high degree of turbulence is eiiected in the mixing operationthereby reducing the overall pump efiiciency. The regular annulararrangement of inlets in the Schutte device further attributes to lowcombining efficiency since mixing occurs only at axially and radiallyspaced intervals along the mixing chamber rather than continuously alongits length.

The primary object of this invention is to provide a highly eflicientjet pump which combines two fluids of substantially equal density byentraining a secondary fluid in a primary fluid in increments along thelength of a mixing chamber under constant or substantially constantstatic pressure conditions whereby losses attributable to expansion ofthe fluids in the mixing chamber are substantially eliminated.

Another object of this invention is to provide a jet pump whichmaintains the static pressure of the drive fluid constant and butslightly above the fluid vapor pressure throughout the mixing chamber toobtain maximum pumping efliciency while preventing cavitation due to avaporization of the motive fluid.

Still another object of this invention is to provide a jet pump havingmeans for feeding secondary fluid into the mixing chamber substantiallyparallel with the axis of the primary fluid flow through the mixingchamber.

Another object of this invention is to provide a jet pump and method ofoperation wherein the relative velocities and flow rates of the driveand driven fluids are coordinated with the configuration and dimensionsof the mixing chamber so that complete mixing of the fluids isaccomplished before interception of the chamber side walls by theexpanding drive fluid.

Yet another object of this invention is to provide a jet pump having adivergent-walled mixing chamber for maintaining substantially constantlow static fluid pressure throughout the chamber.

A further object of this invention is to provide a jet pump havingadjustable wedges for selectively changing the weight ratio of primaryfluid to secondary fluid while at the same time maintaining a highdegree of pumping efliciency.

Another object of this invention is to provide a jet pump havingdiverter vanes mounted on the inner surfaces of the mixing chamberwallsin a position sufficient to direct secondary fluid flow through inletsin the mixing chamber walls substantially parallel to primary fluid flowthrough the mixing chamber.

Yet another object of this invention is to provide a method forentraining a first fluid in a second fluid by accelerating the secondfluid to provide a low pressure region at several locations along theflow of the second fluid and guiding flow of said first fluid into thelow pressure regions at the several locations so that the first fluidtravels substantially parallel with the second fluid providing a largeinterface area between the first and second fluids along which thestatic pressure of the two fluids remains substantially constant.

Still another object of this invention is to provide a cylindrical jetpump which can be operated at efliciencies above 50%, said pump having amixing chamber which converges to a diameter at its downstream end whichexceeds the diameter of the jet discharge orifice for the drive fluid byan amount substantially equal to twice the tangent of approximately 252times the length of the mixing chamber.

Yet another object is to provide a method of operation of a jet pump sothat the weights of the primary and secondary streams and the densitiesof the fluids are correlated with the jet pump dimensions according tothe fiollowing relationship:

2 tan 252 approximately v is the exit velocity of the mixture from themixing chamber in feet per second;

p is the density of the primary and secondary fluids which aresubstantially equal; and

D, is the pump nozzle discharge orifice diameter.

These and other objects of the present invention will become moreapparent from the following description and appended claims when read inconjunction with the accompanying drawings wherein:

FIGURE 1 is a sectional view of a prior art jet pump;

FIGURE 2 is a sectional view of one form of jet pump of this invention;

FIGURE 3 is a top view of the interior portion of the jet pump of FIGURE2 taken substantially along line 3--3 of FIGURE 2;

FIGURE 4 is an enlarged view of the diverter vanes from the jet pump ofFIGURE 2;

FIGURE 5 is a transverse sectional view substantially along line 5-5 ofFIGURE 2;

FIGURE 6 is a top view similar to FIGURE 3 of another embodiment of thejet pump of this invention;

FIGURE 7 is a sectional view of the jet pump of FIG- URE 2 with anadjustable wedge;

FIGURES 8, 9 and 10 are sectional views of other embodiments of the jetpump of this invention;

FIGURE 11 is an axial sectional view of still another embodiment of thejet pump of this invention;

FIGURES 12-15 are transverse sectional views substantially along lines1212 to 15-15 of FIGURE 11;

FIGURE 16 is a plot of the relation of the efliciency of constantpressure mixing jet pumps constructed in accord with the presentinvention to the ratio of their throat and suction velocities;

FIGURE 17 illustrates a test pump set up and the measured and thecritical pressure curves for that pump;

FIGURE 18 illustrates one arrangement for compounding jet pumpsconstructed in accord with the present invention; and

FIGURE 19 illustrates a second arrangement for compounding jet pumpsconstructed in accord with my invention.

Referring to the drawings wherein like numerals are used throughout toidentify like parts, FIGURE 1 discloses a basic prior art jet pumpcomprising a primary motive or driving fluid flow conduit 10 bounded bystraight rectilinear, usually cylindrical side walls 11 which convergeaxially to form a nozzle 12 axially spaced from an entrainment area ormixing chamber 14 having opposed rectilinear side walls 16 and a flangedinlet end portion 18. The space between the tip of nozzle 12 and thesurrounding portions of wall 18 provides an annular inlet throat for thesecondary fluid into the jet pump mixing chamber. As the primary ordriving fluid accelerates to flow through converging nozzle 12, itsstatic pressure decreases. Upon admission of primary fluid into mixingchamber 14, through nozzle 12 its fluid velocity gradually decreasesfrom a maximum at the jet outlet to the velocity of the mixture and itsstatic pressure gradually increases, creating a low pressure region atthe nozzle outlet and a progressively increasing pressure regionthroughout the mixing chamber length (see FIGURE 6, page 177, Universityof California Publications in Engineering, vol. 3, No. 3). The secondaryfluid which is at a higher static pressure than that present in themixing chamber is thus induced into the low pressure region of themixing chamber. The prior art jet pump of FIGURE 1 effects mixing of theprimary and secondary fluids substantially by a batch process, whereinthe secondary fluid mixes with the primary fluid in the mixing chambereffectively only at one axial location. Consequently, turbulence andsecondary flow losses are extremely high.

FIGURE 2 shows a jet pump in accord with this invention. The primary ordriving fluid conduit 19 is axially disposed within a pump housing 21and comprises upper and lower side walls converging axially into nozzle24 which is integral with axially diverging side walls 26 of anentrainment area or mixing chamber 25. The included angle between thewalls 26 is preferably in the order of 6 to 12. Thus, the upper andlower boundaries of the primary flow conduit and the mixing chamber areformed of integral opposed walls having straight sections 20, convergingarcuate sections forming nozzle 24 and diverging wall portions 26 andthe walls 26 are located substantially along the natural angle ofdivergence of the jet and form a physical boundary between the region inwhich the secondary fluid inlet velocity is measurable and the zone ofmixture of primary and secondary fluids.

Secondary fluid flow conduits 23 are formed by the spacing of primaryconduit side walls 20 and housing walls 22. The secondary fluid is at alow energy state in conduits 23 and the primary fluid which is at ahigher energy level imparts its energy to the secondary fluid duringentrainment thereof.

The pump primary conduit and mixing chamber walls may be mounted in thepump housing, as shown in FIG- URE 5, by welding or otherwise attachingthe axially extending side edges of walls 26 in fluid tight relation tohousing 21. Alternatively, integral pump primary flow conduit 19, nozzle24 and mixing chamber side walls 26 may be formed as a unitary castingof cylindrical crosssection which may be mounted within a cylindricalhousing by suitable brackets and supports (not shown).

The mixing chamber side walls 26 are provided with a plurality ofaxially spaced inlets 28 which may be either transversely extendingslots 31 forming an oblique angle with the pump axis as shown in FIGURE3, or spaced through-apertures 32 as shown in FIGURE 6. In theseembodiments, each secondary flow inlet is provided with an axiallyextending fluid diverter vane 30 protruding into the mixing zone andarranged to direct secondary flow substantially parallel to primaryfluid flow through mixing chamber 25. The mixing operation of the jetpump of FIGURE 2 is, thus, continuous and differential wherein thesecondary fluid is mixed with the primary fluid in small incrementsaxially along the mixing chamber. The preferable axial spacing ofopenings 31 or 32 is just sufficient to allow thorough mixing of thesecondary fluid from the first inlet with the drive fluid beforesecondary fluid from the second inlet contacts the drive fluid and so onsuccessively and continuously along the mixing chamber. The exact sizeand spacing of the openings 31 or 32 depends upon the viscosity of thedrive fluid and the pumping velocity, the critical factor being themaintenance of the static pressure within the mixing zone substantiallyconstant along the entire length of the walls 26.

The diverter vanes 30 reduce impact losses between the secondary fluidand primary fluid by lowering turbulence at the points of impact. Thesubstantially parallel travel of the fluids through mixing chamber 25provides a large fluid interface area for mixing without excessiveturbulence.

Each vane, as best illustrated in FIGURE 4, axially tapers in thedirection of fluid flow from the entrance edge 36 of inlet 28 forming anarcuate tapered wedge having be obtained in reducing turbulence andimpact losses by' arranging the slots at an oblique angle to the axis ofthe pump. It has been empirically determined that for most eflicientpump operation, the slots should intersect the pump axis at an angle ofabout 30. Similarly, apertures 32 may be aligned to form rows whichintersect the axis of the pump at an oblique angle. Such a distributionof secondary fluid inlets systematically further increases theprimary-secondary fluid interface area in the mixing chamber to provideoptimum mixing conditions throughout the mixing zone.

Primary fluid flow conduit 19, nozzle 24 and diverging side walls 26 ofthe mixing chamber form smooth curves and may be highly polished topresent substantially frictionless surfaces for low resistance to fluidflow during pump operation if contact occurs. With such construction,the frictional flow losses are substantially reduced over the prior artjet pumps. Energy losses due to expansion of the primary fluid in themixing chamber are substantially eliminated since side walls 26 divergeat about the angle of expansion of the primary stream in the mixingchamber thereby eliminating interception of the side walls beforecomplete mixing is accomplished.

In operation of the jet pump, the primary fluid is initially forcedthrough conduit 19 under a predetermined head provided either by theforce of gravity or an auxiliary pumping unit (not shown). The fluidaccelerates when it enters the convergent section of nozzle 24 becauseof the difference in cross-sectional area between the inlet portion ofprimary conduit 19 and the convergent section of nozzle 24. In jet pumpsutilizing liquids, the exit velocity is chosen slightly below that whichwould reduce the liquid pressure to its flash point or vapor pressure.When the fluids are vapors or gases, I prefer to use nozzle exitvelocities which are slightly subsonic, in the order of 1300 ft./sec.for example, to avoid the problems inherent in supersonic nozzle design.This increase in velocity causes a reduction in the fluid staticpressure pv, which effects a low pressure area surrounding the drivefluid jet as it extends into the mixing chamber. Secondary fluid fromsecondary conduits 23 being at a higher pressure is induced throughinlets 28 into fluid communication and entrainment with the drive fluidin the mixing chamber. The diverging chamber side walls enable thechamber to be so designed that the static pressure of the drive fluid ismaintained constant and if liquids are involved but slightly above theliquids vapor pressure throughout the chamber length to provide a highentrain-' ing force without cavitation or fluid expansion losses.

If the secondary fluid is a condensable vapor such as steam and theprimary fluid a cooler liquid such as water, the steam will condenseupon contact with the water in the mixing chamber. If the steam entersthe mixing chamber at a severe angle to the axis of the water flow, itwill penetrate the water surface and condense in the stream of waterrather than at the interface on the surface of the water stream.Instantaneous condensation of the steam bubbles within the water causeshigh turbulence and cavitation which contribute to extremely lowefliciency of jet pumps. Cavitation is substantially reduced, however,in the jet pump shown in FIGURE 2 by diverter vanes 30 and divergingside walls 26 of the mixing chamber which direct secondary fluid flowsubstantially parallel with the stream of primary fluid in the mixingchamber thereby increasing the interface area between the primary andsecondary fluids and substantially preventing impingement of walls 26prior to complete mixing of the fluids. Arranging slots 31 of FIGURE 3or holes 32 of FIGURE 6 obliquely to the axis of the jet pump, asexplained, creates an even greater interface area between the primaryand secondary fluid thereby further increasing the efficiency of thepump by continuously contacting the upper and lower surfaces of thedrive fluid with secondary fluid. A comparison of FIGURES 1 and 2 showsseveral basic structural differences between the jet pump of the instantinvention and that of the prior art. For example, in the high efliciencyjet pump of FIGURE 2, nozzle 24 and mixing chamber walls 26 are integralsuch that the front throat portion 27 of mixing chamber 25 is the samediameter as nozzle 24. Mixing chamber walls 26 are divergent rather thanstraight thereby providing a greater cross-sectional area for mixing asthe axial distance from nozzle 24 increases and preventing interceptionof the.

chamber side walls before complete mixing is accomplished. Also, themixing chamber is provided with a plurality of secondary fluid inlets 28rather than a single annular inlet such as that between nozzle 12 andside wall edges 18 of the FIGURE 1 prior art pump. Each of the inlets ofthe high efiiciency pump of FIGURE 2 is further provided with a divertervane 30 which directs the incoming secondary fluid substantiallyparallel with the expanding accelerated primary fluid in the mixingchamber thereby providing a greater interface area between the primaryand secondary fluids reducing penetration of the primary fluid into thesecondary fluids and turbulence within the primary fluid. The greatersurface contact area of the parallel streams of fluids enablescondensation to be completed at the interface rather than within theprimary fluid as commonly occurs in prior art pump structures. Eachfeature of the jet pump of FIGURE 2, thus, contributes to the increasesin efliciency over prior art pumps.

It is possible to determine the dimensions for maximum efliciency of thejet pump of FIGURE 2 from a consideration of the energy relationships inthe mixing chamber. From the general energy balance, the sum of theprimary fluid energy and the secondary fluid energy minus the primaryand secondary fluid expansion losses and the primary fluid impact lossesequals the final fluid energy in the mixer exit portion.

The primary fluid expansion loss can be expressed as and the secondaryfluid expansion loss can be expressed as V 2 V Z fag g fdwa) wheresecondary fluid at distance x from the primary fluid nozzle) s=secondaryfluid entrance conditions.

The impact loss for the primary driving fluid can be expressed as p v xs 2 f g dwa where V =secondary fluid velocity, ft./sec. w =secondaryweight flow rate, lb./sec.

The'primary and secondary fluid energies may be expressed according tothermodynamic incompressible fluid flow equations as respectively andthe final output energy in the mixing chamber may be expressed as where:

w=flow rate, lbs/sec.

. p pressure, lbs./ft.

Thus, the energy balance for the jet pump of FIGURE 2 may be expressedas:

y g dw fdw f g dw The general solution to the foregoing energy balanceequation after differentiation and mathematical reduction to lowestterms is:

where c is a constant equal to It has been found empirically that thevalue for at maximum efficiency of the pump is about 6 to 12 (seeApplied Thermodynamics by Faires, pages 142, published by MacMillan Co.,copyright 1936 and 1938). Also at maximum efficiency p v the staticpressure of fluid moving through mixing chamber is a constant valueslightly above the vapor pressure of the primary driving fluid. Thus, byassigning arbitary desired values to the velocities and flow rates, therelative dimensions of the primary conduit, the secondary conduit andthe mixing chamber can be determined for maximum efficiency operation ofthe jet pump.

Although the energy balance equation used as a basis for deriving thegeneral design solution was based on an incompressible fluid behavior,the general solution is valid for a gaseous fluid providing that bothprimary and secondary fluids enter the entrainment area at approximatelythe same temperature.

A jet pump having a square cross-section with an inclusive angle of 6for the diverging mixing chamber side walls and a plurality of slotsarranged at to the pump axis with none of the slots overlapping axiallywas designed using the foregoing design equations and the followingconditions for water as both the primary and secondary fluid:

a primary fluid pressure head of 70 feet measured in feet of waterabsolute (/1 a secondary fluid pressure head of 34 feet measured in feetof water absolute (/1 the flow rates of the primary fluid and secondaryfluid were made equal at 2.4 lbs. per second a final static pressure ofthe mixed fluids of zero (pv=0); a secondary fluid velocity of 46.8 feetper second; and

a primary fluid velocity of 67.2 feet per second.

The designed jet pump for an output of 4.8 pounds per second had a slotdepth of .0614 inch, a nozzle area of .000625 square feet, and a mixingchamber length of 1.44 inches.

Jet pumps normally have an average efficiency value of about 25%. Thejet pump of the above design had an efficiency of greater than 50%. Theefficiency of a jet pump as used for comparison here is defined as theratio of the pumping energy given up by the drive fluid to the pumpingenergy absorbed by the secondary fluid. It is calculated by multiplyingthe ratio of the difference between the fluid head in the mixing chamberand the fluid head in the secondary conduit to the difference betweenthe fluid head in the primary conduit and the fluid head in the mixingchamber by the ratio of the flow rate in the secondary conduit to theflow rate in the primary conduit or expressed mathematically:

As shown in FIGURE 7, a control rod or axially adjustable wedge 48 maybe used in combination with the jet pump of this invention. Adjustablewedge 48 comprises a solid wedge shaped end portion 50 having opposedarcuate surfaces 52 joined to a shaft portion 54. Shaft portion 54 maybe slidably mounted in a suitable fixture such as bracket 56 fixedlymounted on jet pump housing wall 22. Shaft 54 is axially slidable inbracket 56 so that wedge portion 50 can be moved toward and away fromnozzle 24. By selectively positioning wedge portion 50, the weight ratioof the primary drive fluid to the secondary fluid can be selectivelyvaried. Also, the angle at which the primary fluid travels throughentrainment area 25 can be varied, compensating for any variations inthe flow properties of the secondary fluid entering the entrainment areathrough inlets 28. For example, a variation in secondary fluid densitymay cause certain secondary fluids not to flow parallel with the primaryfluid flow since the diverter vanes are designed for a fluid of aspecific density. Thus, by varying the path of the driving fluid, theangular contact between the primary fluid and secondary fluid can stillbe controlled so that the fluids move substantially parallel to eachother providing the desired large interface contact area between thefluids.

Adjustable wedge 48 is also valuable in maintaining a high degree ofefficiency when the weight ratio of the primary drive fluid to thesecondary fluid has been changed, consequently varying the relative flowproperties of the fluids in the mixing chamber. By selectivelypositioning adjustable wedge 48, any changes in the weight ratios of thetwo fluids can be compensated for so that the flow directions aremaintained substantially constant. The beneficial effects of a mixingchamber having diverging walls also can be obtained as shown in FIG- URE8, by varying the inlet configuration for the primary drive fluid. Inthis embodiment of the invention, the primary conduit 119 is enclosed byupper and lower walls 120 integrally connected to a converging nozzleportion 124 which is integrally joined with a pair of drive fluidinjecting unit walls 126 having a plurality of openings 128 therein.Injector walls 126 converge to a wedgeshaped transverse end edge 130.The effect obtained by the diverging mixing chamber walls of the jetpump of FIGURE 2 is obtained in the jet pump of FIGURE 8 by means ofconverging walls 126 which provide diverging low presure mixing zones127 with the pump housing 131. Diverging zones 127 are dimensioned tomaintain a constant static pressure throughout. Openings 128 arepreferably provided with vanes as shown in FIGURE 4 to direct theprimary fluid substantially parallel with the induced secondary fluidflow into low pressure regions 127. In the jet pump of FIGURE 8,secondary flow is induced into the mixing chamber in increments due tothe successive reduction in pressure at axially spaced inlets 128. Aspreviously discussed, fluid mixing occurs at the large interface areabetween the primary and secondary fluids.

Another embodiment of this invention is shown in FIG- URE 9, as having ahousing 132 with straight side wall portions 133, converging wallportions 134 and diverging wall portions 136. The primary flow conduit140 is bounded by walls 142 which are integral with pump nozzle 144. Thesecondary fluid flow conduit 146 is formed between housing straightportions 133 and primary conduit walls 142.

Nozzle 144 is integral with a pair of slightly converging injector walls148 having primary fluid inlets 150 axially spaced therein and angled topermit primary fluid flow into the mixing portion 152 of the pump inincrements as in FIGURE 8. Slightly converging walls 148 and divergingwalls 136 of the pump housing form a pair of substantially divergentmixing chambers 151 therebetween.

Walls 148 of the primary flow injector are integrally joined with awedge shaped block 154 having opposed arcuate surfaces 153 which extendaxially toward the pump outlet providing smooth surfaces for guiding andintermingling mixed fluids from the upper and lower mixing zones as theytravel axially toward the pump out let to the right of FIGURE 9.

In the embodiments shown in FIGURES 8 and 9, it should be clear thateither the drive fluid or the driven fluid may flow through the outerconduit depending on the location of the pump nozzle. For example, asshown in FIGURE 10;, the central conduit may carry the sec ondary fluidfiow and the outer coaxial conduit may carry primary fluid flow. In sucha pump the injector portion 160 is connected directly to the secondaryflow conduit walls 162.

I have further discovered that it is possible to obtain high jet pumpefliciencies without using a plurality of inlets from the secondaryfluid conduit into the mixing chamber and without using a divergingmixing chamber.

It is essential, however, that the pump he closely designed to maintaina constant primary fluid static pressure throughout the mixing chamberand that the expanding drive fluid not intercept the mixing chamber sidewalls prior to complete mixing of the fluids. This embodiment of theinvention is representediin FIGURE 11 which shows acylindrically-cross-sectioned jet pump.

As previously explained (Applied Thermodynamics by Faires, page 142,published by-MacMillan Company, copyright 1936, and 1938) the naturalexpansion angle for fluids, after passing through a constrictive throator orifice, for minimum turbulence is in the orderof 6 to 12".Experiments have shown that in a jet pump, a jet pump, a jet of primaryor motive fluid discharging from a circular orifice into a coaxialmixingchamber will expand in a cone form having an apex angle of 5 44'plus or minus a few minutes, as shown in FIGURE 11, until the peripheryof the expanding jet intercepts the chamber side wall. If the secondaryfluid is induced into the mixing chamber in surrounding relation to theprimary fluid orifice at a lower velocity than the velocity of theprimary fluid, the portion of the chamber between the plane of theprimary fluid orifice and the plane of intercept of the conical streamof primary fluid with the chamber wall will form the mixing zone for theprimary and secondary fluids and at that intercept plane, the mixedfluid will have a velocity determined by the energy of the primary andsecondary fluids as they enter the mixing chamber and the losses withinthe mixing chamber.

In the embodiment illustrated in FIGURE 11, the cylindrical primaryconduit 166 extends through an openi ig in secondary conduit wall 168and is in fluid tight relation with the edges of the opening. Theprimary fluid discharge nozzle 170 has a sharply axially tapered lip 172so that, at the discharge orifice 174, the paths of flow of the primaryand secondary fluids are substantially parallel as in the FIGURE 2, 7, 8and 9 embodiments. The fluid velocities measurable within the mixingzone (the region between the section planes 1212 and 1515) are, asillustrated in FIGURES ll, 14 and 15, in the center; the dischargevelocity of the primary fluid from the jet (V,-) at the periphery; thevelocity of the secondary fluid (V 'as it enters the mixing chamber;and, in between, the velocity of the mixture v(V as it exists at thedownstream end of the mixing chamber as represented by the section plane1515. As is apparent from FIGURES 11-15, the cross-sections of theregions in which the velocities Vj and V exist gradually decrease inarea along the length of the mixing chamber from maximums in the plane12-12 to zero at the downstream end of the mixing chamber in the plane15-15; and the region intermediate the planes 1212 and 1515, thecrosssection in which the velocity V exists, gradually expands incross-section from a continuous line at the plane 12-12 of the primarynozzle until it is equal in crosssection to the cross-section of themixing chamber at its downstream end in the plane 15-15.

I have found that, if the mixing chamber is properly designed for therequired flow conditions so that the static pressures, pv (where p isthe pressure in pounds per square foot and v is the specific volume incubic feet per pound), are constant, for example, and if the primary,secondary and mixed stream are equal and constant (p -v =p v p v =c),the boundary layers 176 and 178 between the regions in which thevelocities V V and V exist throughout the mixing chamber are quitesharply defined and the efiiciency of the jet pump is, as a result,greatly increased.

For blunt enclosed nozzles, a region of turbulence exists at-the initialjuncture of the primary and secondary streams. While the configurationsof the regions in which the velocities V and V exist in the mixingchamber remains substantially the same as illustrated in FIGURES 12-15,the Value of the velocity V within-the intermediate region betweenboundary layers 176 and 178 is not uniform n-or, except at thedownstream end of the mixing chamber (the plane 1515), equal to thevelocity V The velocity within this region between boundary layers 176and 178 is a diflerential variable (dV gradually increasing in valuefrom the plane 1212 of the jet orifice to the value V at the plane 1515at the 'downstream end of the mixing chamber. As a result, the losses inthe mixing chamber are higher when a blunt end nozzle is used than whena sharply tapered nozzle as illustrated in FIGURE 11 is used.

I have found that the static pressure pv within the mixing chamber canbe maintained constant if and only if the wall 180 of the mixing chamberconverges throughout its length between the planes 1212 and 1515, i.e.,if the mixing chamber is of gradually decreasing cross-sectional areanormal to the jet axis from the plane 12-12 of initial intermixture ofthe primary and secondary fluids to the plane 1515 of intercept withthechamber wall of the lines tangent to the primary jet orifice andintersecting'the jet axis at an angle of about 544. (as indicated by theconical boundary layer 176), i.e., the plane at which the streamdischarged from the nozzle would normally intercept the chamber wall.Considered another way and applied specifically to orifices and chambersof circular cross-sections about a common axis, as illustrated inFIGURES 12-15, the mixing chamber must converge throughout its lengthfrom plane 1212 to plane 15'15 and have a diameter D, at its downstreamend at the plane 1515 which exceeds the diameter of the dischargeorifice for the primary stream D, by an amount in the rangesubstantially equal to twice the tangent of 252 times (i.e.,approximately .10014 times) the length of the mixing chamber. Statedmathematically, D =D +2 tan (252')x. When this relation exists, the jetpump can be operated at efiiciencies above 50% as compared with a normal20 to 25% efiiciencies found in jet pumps, see Mechanical EngineeringHandbook by Marks, 5th edition, McGraw-Hill Book Company, at page 1833.

The design equations for a pump of the type of FIG- URES 11-15 follows.The General Energy Equation for a standard jet pump having a parallelsided mixing chamber is: primary fluid energy+secondary fluidenergyimpact lossexpansion lossfriction loss=mixed energy. Statedmathematically:

The friction loss may be ignored providing V is small. Since thesecondary fluid is the fluid that rubs the sides of the mixing chamberand it is constant throughout the mixing process it can be computedreadily if V is larger.

Ignoring friction loss and solving the energy equation for the pump ofFIGURE 11 it reduces to:

When W W V V are selected for design condition this equation is solvedfor V V is the velocity after the primary and secondary fluid are mixed.

When V is determined the area of the throat is:

(w.+ws)

The diameter of the throat then is:

Solving for V, by quadratic equation:

v 70 F. for water=.01606 fb.

A .00260045 ft.

=.0047s94 it.

Total area=A,-|A,=.68968 in. +.l1946 in.

Inlet total diameter= =l 015 in 3.1416

Since p v =p v =p v for a constant pressure mixing process,

Efficiency-- v2 Eflicieney For w -w,,

V-V., 2 2 From General Energy Equation solving for VP,

Efficiency V mV Substituting,

2 2 Efiiciency= (mvs) 5 It should be noted, as is apparent from FIGURE16, that when the V,/ V ratio (m) is infinite, the efficiency is 50.0%.1

As proof of the foregoing theory, I have constructed a jet pumpsubstantially in accord with FIGURE 11 but with a straight section ofuniform cross-section interposed between the mixing chamber and thediffuser as is illustrated at the top of FIGURE 17. FIGURE 17 pro- 20vides a comparison between the theoretical pressure curve and the actualmeasurements which were made.

For this test of the constant pressure mixing pump illustrated in FIGURE17, the inlet pressure was 20.5 p.s.i.g.; and at the flo-W orifice, forthe primary fluid 25 Ap"H =4.8 and for the secondary fluid ApH =4.8.

The total flow by weight measurement was 332 min.=39.6 g.p.m.

The pressure reading, which are plotted in the center of FIGURE 17,were:

7. It will be noted that there is a dotted path between pressure tap No.6 and pressure tap No. 7, since I am not quite sure of the pressure plotbetween these two plots. However, from past testing I know basicallywhat is happening. The location of the throat in this test model is notquite properly located from the nozzle. The throat location is too faraway and the natural expansion of the primary jet has intercepted thesides of the mixing chamber before the throat is intercepted. Thiscauses an over expansion of the primary jet and an expansion loss.Immediately after the interception of the mixing wall by the primary jetthere has to be a contraction or the mixture has to speed up therebydecreasing its static pressure in order to go through the smaller areaof the throat. From pressure taps No. 7 through No. 10 the mixture isgetting back to equilibrium conditions after the contraction. Frompressure tap No. 10 to No. 11 is the standard pressure loss due tofriction. The reason why the pressure did not go back to approximatelypressure ft. H O gage at pressure tap No. 10 is due to the friction lossbetween pressure tap No. 7 and pressure tap No. 10 and the slightexpansion loss experienced by the main or primary fluid jet overexpanding.

From past experience a correction of .050" or less in throat locationwill correct this situation.

This difference between the theoreticaland test curves does not indicatean error of any appreciable magnitude in the formula for mixing lengthbut rather the critical importance of departures from it. For example,if the primary fluid jet nozzle is not accurately aligned with thePress. Tap No 1 2 3 4 5 6 7 8 9 10 11 "H 15 10 0 1. 9 2. 4 2. 3 1. 9 2.2 Ft. H 0 17 113 0 227 283 283 2. l5 2. 72 2. 61 2. 15 2. 49

The jet and throat velocities were:

Jet velocity 20.0 g.p.m., design 53.8 ft./sec., actual 53.84 ft./sec.

Throat velocity 40.0 g.p.m., design 34.35 ft./sec., ac-

tual 34.35 ft./sec.

From the measured data:

The actual efliciency was therefore:

w,(H.-H, 2.781(16.20 1.52 Emc1ency w, (H, H. 2.7s1 44.97 16.20)

The V /V ratio was:

3.005" from the nozzle or at .005" past pressure tap No.

axis of the mixing chamber, then there will be an interception of themixing wall by the primary fluid before the throat is reached. Also, asindicated above, the theoretical angle of expansion of the primary jetas found experimentally by myself of 5 44' may be a few minutes inerror.

It will be noted from FIGURE 16 that the test pump gave an efliciency of51% as opposed to 63% from the theoretical efficiency at a V V ratio of3.69. By properly locating or adjusting the throat location anefliciency of 63% would have been obtained.

A straight section after the convergent mixing section was included inthe test pump illustrated at the top of FIGURE 17 to detect if thethroat location was correct. In an actual jet pump with proper throatlocation this straight section is unnecessary as indicated in FIGURE 11.

The jet pump as depicted in FIGURE 11 and expanded upon in FIGURE 12through FIGURE 15 is superior in all cases to the differential jet pumpdepicted in FIG- URE 2 through FIGURE 10. There are two reasons forthis: (1) the FIGURE 11 pump is easier to build and design, (2) of thetwo losses (neglecting friction) occurring in a standard jet pump,expansion loss and impact loss the pump of FIGURE 11 completelyeliminates the expansion loss and the differential pump of FIGURES 2-10does not completely eliminate it. 7

Since the pump of FIGURE 11 completely eliminates the expansion loss andonly the impact loss is left, by compounding the pump of FIGURE 11 theefliciency of this pump may be increased at any V /V ratio and the 15impact loss may be reduced thereby. This may be done in the mannerillustrated in FIGURES 18 and 19.

As indicated above, the efficiency of the FIGURE 11 jet pump isdependent only upon the V,,/ V ratio for any particular w /w ratio andthe loss is impact only at The closer the V /V ratio becomes to unity,the higher the efliciency will be. For any particular V V ratio for asingle stage, the ratio may be made more nearly unity by compounding thepump and still operating at the overall V /V ratio for a single stagepump, thereby increasing the efliciency as graphed for a single stagepump in FIGURE 16.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiments are therefore to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription, and all changes which come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States LettersPatent is:

1. The combination in a jet pump or the like of axially elongatedhousing means, means providing a first fluid conduit means in saidhousing means, means providing a second conduit means in said housingmeans in overlying relationship to said first conduit means, means forelfecting flows of primary and secondary fluids through said first andsecond conduit means, means providing in said housing means a divergingmixing chamber for the primary and secondary fluids, means foraccelerating the primary fluid and directing said accelerated fluid fromthe conduit means in which it is flowing into said diverging mixingchamber at the upstream end thereof, means for introducing the secondaryfluid into said diverging mixing chamber for entrainment by the primaryfluid in distinct increments at intervals spaced along said mixingchamber and in a direction substantially parallel to the flow of primaryfluid, said mixing chamber being dimensioned to maintain the staticpressure on the fluids flowing therethrough substantially constant fromthe upstream end thereof to the downstream end thereof and the angle ofdivergence being approximately equal to the angle of expansion of theprimary fluid in said mixing chamber to minimize energy lossesattributable to expansion of the primary fluid; and discharge meanscommunicating with the downstream end of the mixing chamber forconducting from said chamber the primary and secondary fluids introducedtherein from said first and second conduit means.

2. The combination of claim 1, wherein the mixing chamber providingmeans comprises a diverging apertured member extending from the outletof the first fluid conduit means generally to the downstream end of theflow passage in said housing means and flow directing means on saidmember adjacent each of the apertures therethrough for directing fluidflowing from said second conduit means through said apertures into saidpassage into contact with the fluid flowing into said passage from saidfirst conduit means in streams which are generally parallel to thelongitudinal axis of the flow passage.

3. The combination of claim 2, wherein the apertures in said divergingmember are oriented at an oblique angle relative to the longitudinalaxis of the flow passage.

4. The combination of claim 1, together with means disposed in saidhousing means for selectively varying the ratio of primary fluid tosecondary fluid in the fluid flowing through the mixing chamber.

5. The combination of claim 1, wherein the angle of divergence of saidmixing chamber is in the range of from about 6 to about 12.

6. The combination in a jet pump or the like of axially elongatedhousing means, a first fluid conduit means having an outletcommunicating with the interior of the housing means at a first,upstream end thereof, a second fluid conduit means having an outletsurrounding the outlet of the first conduit means, said second fluidconduit means communicating with the interior of the housing means atthe upstream end thereof, means for eifecting flows of primary andsecondary fluids through said first and second fluid conduit means intosaid housing means, means including a converging section of said housingmeans for providing in said housing means a primary and secondary fluidflow passage having an inlet communicating with the outlets from thefirst and second fluid conduit means and for maintaining the staticpressure exerted on the fluid therein generally uniform the length ofthe passage, and discharge means communicating with a second, downstreamend of the housing means for conducting from said flow passage theprimary and secondary fluids introduced therein from said first andsecond conduit means.

7. The combination of claim 6, wherein the diameter of the downstreamend of the covering housing means section exceeds the diameter of theoutlet of the first conduit means by an amount in the range of one-tenthof the length of the converging section.

8. The combination of claim 6, wherein said first conduit meansterminates in orifice means capable of producing contact of the primaryand secondary fluid along interfaces which are generally parallel to theconverging section of the housing means and thereby minimizingturbulence-induced energy losses in said flow passage.

9. A multistage jet pump or the like in which the initial stagecomprises housing means, a first fluid conduit means having an outletcommunicating with the interior of the housing means at a first,upstream end thereof, a second fluid conduit means having an outletsurrounding the outlet of the first conduit means, said second fluidconduit means communicating with the interior of the housing means atthe upstream end thereof, means for effecting flows of primary andsecondary fiuids' through said first and second fluid conduit means intosaid housing means, means for providing in said housing means a primaryand secondary fluid flow passage having an inlet communicating with theoutlets from the first and second fluid conduit means and formaintaining the static pressure exerted on the fluid therein generallyuniform the length of the pas sage, and in which each succeeding stagecomprises housing means, fluid conduit means having an outletcommunicating with the interior of the housing means at a first,upstream end thereof, means for effecting a flow of fluid through saidfluid conduit means into said housing means, means for providing in saidsucceeding stage housing means a primary and secondary fluid flowpassage having an inlet communicating with the outlet from the fluidconduit means and for maintaining the static pressure exerted on thefluid therein generally uniform the length of the passage, and meansproviding fluid communication between the upstream end of said flowpassage and the downstream end of the primary and secondary fluid flowpassage of the preceding stage, and including discharge meanscommunicating with a second downstream end of the housing means of thelast stage for conducting from the flow passage thereof the fluidintroduced therein.

10. The multistage jet pump of claim 9, wherein there are at least twoinitial stages as aforesaid, the downstream ends of the primary andsecondary fluid flow passages of said initial stages being connected inparallel to the upstream end of the primary and secondary fluid flowpassage of the succeeding stage of the pump.

11. The combination in a compound jet pump or the like of axiallyelongated housing means, a first fluid conduit means having an outletcommunicating with the inten'or of the housing means at a first,upstream end therea second fluid conduit means having an outletsurrounding the outlet of the first conduit means, said second fluidconduit means communicating with the interior of the housing means atthe upstream end thereof, means for effecting flows of primary andsecondary fluids through said first and second fluid conduit means intosaid housing means, means for providing in said housing means a seriesof primary and secondary fluid flow passages of successively smallercross sectional area and for maintaining the static pressure exerted onthe fluid therein generally uniform the length of each said passage, thefirst of said passages having an inlet communicating With the outletsfrom the first and second fluid conduit means, and each succeeding flowpassage having an inlet communicating with the outlet of the precedingpassage, and discharge means communicating with a second, downstream endof the housing means for conducting from the last of said flow passagesthe primary and secondary fluids introduced into said housing means fromsaid first and second conduit means.

References Cited UNITED STATES PATENTS Re. 19,581 5/1935 Justheim 230-92561,160 6/1896 Du Faur 230-92 571,022 11/1896 Schutte 230-95 580,7624/1897 Brooke 103-265 904,276 11/ 1908 Prache 230-95 1,228,608 6/1917Scanes 230-95 1,936,246 11/1933 Carter et a1. 230-92 2,172,522 9/1939Sline 230-95 2,180,259 11/1939 Sargent 230-95 15 3,123,285 3/1964 Lee230-95 DONLEY J. STOCKING, Primary Examiner.

W. I. KRAUSS, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,371,618 March 5,

John Chambers It is certified that error appears in the above identifiedpatent and that said Letters Patent are hereby corrected as shown below:

Column 6, line 19, for column 7, about lines 24 to equation reading ZV-Vsame c61umn 7, line 38, for line 66, for

"increases" read increase 32, for that portion of the read "pages" readcolumn 12 Column 15 line 22 for "covering" read converging Signed dsealed this 24th day of June 1969.

2 V =ZV V read (SEAL) Attest:

Edward M. Fletcher, J r.

WILLIAM E. SCHUYLER, JR.

Attesting Officer Commissioner of Patents

